"The story of Wool takes place on a decimated Earth, ravaged by some yet-to-be-revealed catastrophe. Humanity clings to survival in the Silo, a subterranean city extending hundreds of stories beneath the surface. There is one paramount law within the Silo: never say you want to go outside, for if you do, you will get your wish."
I just bought the omnibus (books 1-5) this morning for $5.99. The author self-published it through Amazon and so far it’s REALLY good.